Silodosin, the chemical structure of which is represented by means of formula (V) below
is an α-adrenergic receptor antagonist selective for α1A adrenergic receptors that are mainly located in the prostate, the base and neck of the bladder, and the prostatic capsule and urethra. Blocking these receptors causes smooth muscle relaxation which reduces bladder outlet resistance without affecting detrusor smooth muscle contractility, improving storage (irritative) symptoms and emptying (obstructive) symptoms associated with benign prostate hyperplasia. Silodosin has a substantially lower affinity for α1B adrenergic receptors located in the cardiovascular system. Due to these characteristics, silodosin is used in the treatment of signs and symptoms of benign prostate hyperplasia.
Silodosin, the preparation method thereof, and the therapeutic use thereof are described in patent document EP 0 600 675 A1. The methods described in this patent document involve the alkylation of primary amine derivatives either with a halogenated derivative or with an activated alcohol in order to yield a secondary amine intermediate and to then convert same into silodosin. To purify the intermediate and end products in the preparation of silodosin, patent document EP 0 600 675 A1 describes the use of column chromatography, which entails a drawback for carrying out the method on an industrial level.
Silodosin production methods which avoid using steps of purification by means of column chromatography have been described. In this sense, patent document EP 1 806 340 A1 describes the formation of an oxalate salt of the compound of formula (II) (an intermediate in silodosin synthesis)

Patent document EP 1 806 340 A1 describes the production of the compound of formula (II) by means of an alkylation reaction of the amine of formula (III)
with a compound of formula (IV)
wherein LG is a leaving group; and subsequent conversion of the compound of formula (II) that has been obtained into silodosin. The method described in patent document EP 1 806 340 A1 comprises the formation of the oxalate salt of the compound of formula (II), which is a solid that can be isolated by crystallization, and can therefore be separated from the impurities that remain dissolved in the reaction medium.
Patent document WO 2012/147019 A1 describes a similar method comprising the formation of the tartrate salt of the compound of formula (II), also in solid form.
There is a need to provide alternative methods for silodosin synthesis which allow obtaining said product on an industrial scale, facilitating the steps of purification and manipulation of the method.